1. Field of the Invention
The invention pertains to chemicals for herbicidal use.
2. Description of the Prior Art
Although 2,4-dichlorophenoxy acetic acid (2,4-D) and 4-chloro-2-methylphenoxy acetic acid (MCPA) and the esters and salts of these compounds are well known, commercially available, herbicides widely used for control of broadleaf weeds, such compounds ahve demonstrated no discernible herbicidal effect on wild oats (Avena spp.) at rates of application normally used for broadleaf weed control in the presence of economic crops. By itself, this observation would not be considered particularly important, since one would normally expect that a compound could be found which would provide adequate wild oat control, and that a mixture of said wild oat herbicide and the phenoxyacetic acid, ester or salt, would then provide effective control for both wild oats and broadleaf weeds. Unfortunately, however, the problem is not quite so simple.
Wild oats (Avena spp.) are of the family Graminae, the same family in which the small grains, such as wheat and barley are classified. They react to most chemicals in the same manner as the other members of the family, and thus are particularly difficult to control in the presence of economically important grain crops in said family. It is not, therefore, surprising that a considerable effort was required to find several chemicals which provide the selectivity required to achieve wild oat control in the presence of the grains mentioned. The most widely accepted of these are 4-chloro-2-butynyl N-(3-chlorophenyl)carbamate (BARBAN) and the ethyl ester of N-benzoyl-N-(3,4-dichlorophenyl)alanine (SD-30053). They are very effective wild oat control agents when used alone, but unfortunately, when they are combined with the most widely accepted of the systemic or hormonal broadleaf herbicides utilized in the cultivation of small grains, i.e. 2,4-D, MCPA and the esters and salts thereof, the compounds are antagonistic and wild oat control is lost.
These findings are well documented in the literature in articles, such as have appeared in Weeds Today, pg. 13, July of 1970, or in the following articles: "Studies of Barban Selectivity for Wild Oat in Wheat," R. W. Neidermyer, Fargo, North Dakota, Dissertation Abstr. Intern. 31, No. 11, 6383-B-84-B, 1971; "Antagonistic Effect of 2,4-D Amine and SD-30053 on Wild Oats," D. R. Colbert and A. P. Appleby, Corvallis, Oregon, Res. Prog. Rept. West. Soc. Weed Sci., March, 1972, 118-119; "SD-30053 Plus Broadleaf Herbicides," John D. Nalewaja, The Research Report of North Central Weed Control Conference, 1971, pgs. 32-33; "In General, Members of the Grass Family are Resistant to 2,4-D While Most Broadleaf Plants are Susceptible," Weed Control, Robbins, Crafts and Razner, page 9, McGraw Hill, 2nd Edition, 1952; and "Wild Oats are Resistant to 2,4-D," Weed Control as a Science, Klingman, page 388, Wiley, 1961.
In the light of the fact that few compounds have been found which provide selective control of wild oats in the presence of grass grain crops, and further that the most widely accepted of those which are selective are inactivated when combined with the broadleaf control agents, 2,4-D an MCPA, it is surprising to find a compound (i.e. a 1,2-dialkyl-3,5-diphenylpyrazolium salt) that is selective for control of wild oats and also exhibits enhanced wild oat activity when used in combination with systemic or hormonal broadleaf herbicides, i.e. 2,4-D, MCPA or the esters, salts or mixtures thereof.